Surge-proof transformer.



C. H. THORDARSON.

SURGE PROOF TRANSFORMER.

APPLICATION FILED 00L@4 IsIs.

Patened Nov. 16, M15.

2 SHEETS-sun I,

"lllllralu,

C. H. THORDARSON.

SURGE PROOFTRANSFORMER.

APPLICATION mw ocr. s, 1913.

2 'SHEES-SHEE] 2.

' Iioof Transformers; and I -vice or machine out of commission.

CHESTER H. THORDERSON, 0F CHICAGO, ILLINOIS.

SURGE-PROOF 'IRANSFOBMER.

Y v Specificaton'of Letters Patent.

,Patented Novio, i915.

Appiicat'ion flied october e, 1913. seri-aim. 793,787

To all whom 'it may concern.'

Be it known that Dansox, a citizen 'of the United States, and a residentvof Chicago, in and State of Illinois, have invented certain new anduseful Improvements in Surgeclare that the following is a exactdescription thereof, had to the accompanying drawings,` and to thecharacters of reference marked thereon, which form a part of thisspecification.

This invention lrelates to a novel method of protecting electricalmachinery and devices used in electrical power transmission service, andespecially high potential transmission lines, to safeguard the same fromhigh potential disturbances or surges that may occur on the line andprevent the insulation between the turns of the winding of theelectrical device or machine from being burned out, with the result ofputting the de- Such potential disturbances may occur from externalsources, such as from lightning, or from internal potential changes onthe line itself upon the opening of a circuit, or upon the shortcircuiting of the line or portion of the line in which the electricaldevice or machine is connected. Such rapidly changing magnetic flux hasthe effect of producing a potential in all the conductors that lieparallel to it, and, inasmuch as this induced potential is in proportionto the velocity of the surge and its magnetic density, it is evidentthat such induced pressure in the neighboring conductors, lying nearthereto, may become enormously high.

The phenomenon of a break down in tlie insulation ,in high potentialcoils and trans- `foi-mers from an Velectro-magnetic surge is comparableto that. of rthe receiving instru- 'ment ofi-a wireless*telegraphicsystem.

The coherer acts as an insulation vair gap in the in the manner oftheinsulation between the turns of the wire in a high potential transformercoil. The magnetic disturbances of a sui-ge in an aerial system set up apotential on the conductor leading to thecohei'er that is suflicientlyhigh to break through the air gap of the coherer or its insulation andthereby furnisha path for the battery' current to flow to transmit asignal. lLikewise, an excessive surgev in the transformer acts to set upaihigh potential difference in the neighboring turns of' its winding andwhen I, CHESTER H. THoR-' thecounty of Cook do hereby der full, clear,and, reference being` it is suihcientlyhigh to break through the'insulation surrounding these conductors, the exciting potential andcurrent from the magnetic field -of the transformer immediately followthisvpath through insulation and very quickly heat the con: ductor tosuch an extent that'the insulation surrounding it is charred. Thesurgeenergy `bi'eaks down the insulation in the neighboring turns whichis quickly transmitted to each of the turns of the coil with the resultof ruining the transformer.

It has heretofore been lproposed to protect transformers and otherelect/tical devices in high poten-tial power transmission lines byplacing choke or impedance coils in the line in series withthe'electrical devices or machinery to be protected. This method has notbeen .found to meet the requirements for the reason that if the surgeenergy be very high, it may jump around or over the coil, Vand alsobecause it checking to some extent or holding back the energy from thewindings of the devices to be protected, so that the surge energy iallowed to surge back and forth on the line until it is dissipated asheat.v Other practical economical disadvantages work against the luse ofa choke or impedance coil thus arranged. I propose, as a novel method ofsafeguarding electrical devices and machine'i'y from such troublesomeform of energy, and-neutralizing its effect on the transmission system,to apply afew turns of special .winding about the magnetic circuit ofthe transformer or equivalentpart of an 'electrical device to which theinvention may be applied. said winding being connected to the outsideend or ends of the high potential winding of the transformer or otherelectrical devices or machinery. These special turns .ire intended tolie near or parallel to the high potential windingsof the transformerand like windingsinfsiiiiilar devices to be protected,anda'i'efi'i'i'sulated from each other to protect adjacentyturns againstthe induced potential due to such external or internal disturbances. Byplacing an adjustable resistance on the second turn of this specialwinding, the surge ,energy induce in said winding may be dissipated int-lie i' in of heat in saidexteri'ial resistance. and anyvelectro-magnetie energy due to the surge ,which passes still Afartheron may be absorbed in another resistance placed on the third turn, andso on.l The turns of the said the broken down is only efficient mspecial winding are made of progressively increasing cross section andcapacity so as tol s afelytake up the increasing potential impressedthereon by thesurge disturbances, and thereby protect thev electricaldevice from an overcharge of potential, such Vas wouldbreak through theinsulations" between the turns thereof. The number of turns to be used.and the resistance to be employed in connection therewith. maybeladjusted to 'suit the conditions. and,in any event,will

be proportioned as to protect the windings t the electrical devices fromany expected maximum surge. The t amount of surge energy that can bethus dissipated may vary nearly as the square of the induced potentialor many times higher than the operating potential of the magneticcircuit 'of the said electrical device.

l have shown in the'drawin-gs the adapta titan of my invention -to ahigh potential transformer. and havel also shown two different forms ofspecial winding referred to. but 'it will be obvious that the details ofthe application of the invention may be considerably varied within thespirit and scope of the invention.

As shown in drawings: Figure 1 is a vertical section of a high potentialtransformer equipped with my surge protecting` device Fig. 2 is afragmentary section of a transformer et uipped with another form ofsurge protecting device. Fig. 3 is a fragmentaryY section taken on theline 3 3 of Fig. 2. Fig.

' L is a diagrammatic view illustrating the essential electricalelements of the device.v

apart from the mechanical embodiment thereof.

Inthe present instance. said low and high potential coils compriseribbon like conductors with the turns thereof insulated by strips ofpaper. or the like. such. for instance. as are shown in my co-pendingapplication for U. S. Letters Patent. Serial No. 776.521 filed on the30th day of June. 1912)). The magnetic circuit 10 embraces a core member14 about which the low and high potential windings are wound, togetherwith end members 15 and the side members 16 to complete the magneticcircuit. The low potential winding is insulated from the core meinbei'1l by an insulating layer 2f) and is insulated from the high potentialwinding by a thicker insulating layer 21.

Arranged at one or both ends of the core 14 are the lrotective `windingsembodying my inventioiil and designated. as a whole, by

One of s1 cli windings is shown diagrammatically in l"ig. 1 and twodifferent forms or modificatibns thereof arei Sliwn mechanically relatedto other parts inpu'ts 1, 2 and `of the high potential winding 12.

-F ig. 1 comprises five turns, designated respectively as a., b, C, (Iand e. with the turn a leading to af terminal 25 adapted for connectionto the transmission line and with the last turn e connected to theadjacent turn Y In the form of the protective winding shown in saidFig. 1. the said turns are concentrically related.l That is to say. thecenter turn a., comprising a solid conductor. is inclosed within the,next adjacent tubular turn l), with an insulating tube a between them.The said turn b is likewise inclosed within ,the .tubular turn c with aninsulating tube 1)',

and surrounding 4concentric turns are connectedtogether to constitute acontinuous coil or winding bythe connecting conductors a2, b2, c2, and(Z2 as shown in Fig. 1, this arrangement constituting in effect acontinuous spiral coilV which is diagrammati-` cally illustrated in Fig.l as aA conventional winding or coil but of progressively increasingdiameter as it approaches the high tension winding. The said tubularconductors vare preferably made of copper tubing of proper gage. Shuntedbetween the second and third turns of this winding. as well as thefourth and fifth turns. and between like relationed turns of` a longerwinding, if employed. are resistance elements 28. 28. showndiagrammatically in Fig. l. In the mechanical application of theseresistance elements to the turns shown in Fig. 1. they each compriseupper and l-ower conductor plates 26. 2T. connected at their peripheriesby resistance elenient-sl 28. The plates associated with one pair ofresistance elements. (the upper plates as-herein shown) are invelectrical contact with conductors f that are sliunted across the turns7) and c of the protective winding by the conductors b3 and cf. rllheplates 26, 27 of the other pair herein shown are likewise in electi'i'al contact with other tubular conductors f2, fr. rf lpectively. whichlatter are in like manner shnnted i across the turns and c of theprotective winding by the conductors f7". c". These conductors of theresistance circuit are concentrically arranged. in the saine manner asare the turns of the protective winding. the outer conductors being madehollow to inclose the progressively smaller inner conductors and thecentral conductor which is connected to the terminal of the coil. is asolid wire. The several conductors are insulated from each other bytubular insulating sleeve shown The outer conductor f3 is surrounded bya' insulating sleeve or'tube f4, and is finally protected by aporcelain'or other insulating inclosure f5 that is screw-threaded in thetop wall 30 of the casing 31 that inclosesthe transformer elements, andalso a body of ,cooling liquid, as oil, in which the transformerelements are immersed. The turn e of the protective winding isconnectedto the adjacent winding 12 `by a conductor e4.

In the construction shown in` Figs. 2 and 3, the turns of the protectivewinding 35, instead of being arranged concentrically with respect toeach other, are arranged in flatwise relation to each other, the initialturn g being of smallest cross section and the turns toward the highpotential winding being of progressively increasing cross section andcapacity. This relation is best shown in Fig. 3wherein g, g', g2, g3 andg4 designate the respective turns of the protective winding, the initialturn g being made smallest, and the' last turng4L of the windingbeing'made widest to take care of the progressively increasing potentialfrom the 'initial to the lastturn of the winding, in the same generalmanner as the concentric .turns of the winding shown in Fig. 1. Theseveral turns of the winding are insulated from each other by suitablyheavy insulation. The group of windings is inclosed in a heavyinsulating sheath that also serves to hold them together. The turn q ofthe winding 35, last described, is adapted to lead to a suitableterminal of the transmis` sion line. The several'turnsof the saidprotective winding are connected together to complete the coil by theconductors g, g?, g8 and g5" and are also connected by shunt conductorsto the conductors h, h', h2 and h3 of external resistance circuits,herein shown as made of the same constructionas in the type shown inFig. .1.

The construction shown in Figs. 2 and 3. while efficient for the purposedesigned. does not reach the theoretical efficiency of the constructionshown in Fig. 1, inasmuch as the potential generated between the .turnsof the windings acts from a given turn in all directions, and is,therefore, taken up in a more efficient degree in the concentricrelation than in the construction whereinthe turns are arranged side byside. as shown in Figs. 2 and 3. The concentric form is also preferablefor mechanical reasons linasmuch as it is stronger and the windings arenot subject to the liability of spreading apart under theelectro-magnetic stresses which occur in a winding made of flat strips.rl`he same electrical and mechanical advantages appear in thearrangement of the terminal end of the protective winding and .theconductors of the resistance circuits. However. it isto be understoodthat the latter construction may be varied within the broader aspect ofthe inve.n ti on is shown'diagrammatically in order to'clearly trace theconnections. Itwill be understood, however, that all parts of the turnsof the windings and' said conductors at said connections will besuitably covered by heavy insulation andthat the connections betweensaid parts may follow any approved practice.

It will, of course, be understood that the protective winding may andusually will be arranged at both ends of the windings to lbe protectedin order to protect the latter winding from s urges entering the coilfrom either direction.

It will be understood that the details of applying myV novel surge proofmethod or means to the protection of electrical devices or machines intransmission lines may be varied within the scope of the invention, suchdetails depending to an extent upon the specific character of the.machine or device to be protected.

I claim as my invention:

1. The method of protecting the secondary winding of electricalVtransformers which consists in arranging in series with said winding aprotective impedance winding and connecting an external'resistanceacross the turns of said protective winding.

'2. A surge-proof electro-magnetic device comprising, in combinationwith a magnetic circuit, and a winding thereon, of a plurality ofprotective turns connected in series with said windings, wound also uponsaid circuit. and means for dissipating' the energy generated in saidprotective turns.

3. A surge-proof electro-magnetic device comprising. in combination witha magnetic circuit. and a winding thereon. of a plurality of protectiveturns of progressively increasing capacity connected in series with saidwindings and wound also upon said circuit and means to dissipate-theenergy generated in said protective turns.

4. A surge proof electrical transformer comprising` in combination withthe 'inagnetic circuit thereof, and a high potential winding thereon, ofa plurality of imped- A ance windings in series with said high potentialwinding comprising a plurality of turns of progressively increasingcapacity. and means to dissipate the energy generated in the turns ofsaid protective winding.

A surge proof electrical transformer comprising. in combination with'themagnetic circuit thereof, and a high potential windingthereon. of aplurality of impedance windings in series with said high potentialwinding comprising a plurality of turns of progressively increasingcapacity. and external resistance elements connected across the turns ofsaid protective windings.

6. A surgeproof electro-magnetic device gressively comprising` incombination with a magnetic circuit, and a winding thereon, of aplural-` ity of protective'turns of progressively in-v creasing capacityconnected lin series with -said windings and also vvound upon saidcircuit. and external resistanceelements connected across the turns ofthe protective' Winding.

7. A surge proof electro-magnetic device comprising. in combination witha magnetic circuit. and a high tension Winding thereon, of an impedancewinding consisting of a plurality of protective turns. arrangedconcentrically one ivithin the other and of pro-. increasing capacityand separated by tubular insulation and means to dissipate the surgeinduced energv generated in said protective turns. y

S. A surge proof electro-magnetic device comprising'. in combinationWith a magnetic circuit. and a hil of an impedance winding consisting ofa plurality of protective turns` arranged concentrically one Within theother and of progressively increasing capacity and separated by tubularinsulation and external resistance elements connected.across the turnsof saidv protective Winding.

9. A surge proof electro-magnetic device comprising. in combinationvwith a magnetic circuit. and a Winding thereon, of a plurality ofprotective turns of progressively increasing' capacity connected inseries with said Winding and Wound also upon said circuit. and means todissipate the energy generated in said protective turns, said protectiveturns being arranged concentrically one Within another and separated bytubular insulation.

10. A surge proof electro-magnetic device comprising, in combinationwith a magnetic circuit, and a Winding thereon, of a plurality`ofprotective turns ofvprogressively increasing capacity connected inseries with the said Winding and' wound also upon said circuit, means todissipate the energy generated inT said protective turns and externalresistances connected in .shunt betvveen the protective turns. theconductors of said external resistances being concentrically relatedwith one conductor `within another and suitably insulated.v v

1l. A surge proof electro-magnetic device gh tension winding thereon,

comprising, in combination with a magnetic circuit. and awindingthereon, ot' a plurality of protective turnsfof progressivelyincreasing capacity connected in series with the said winding and woundalso upon said circuit, means to dissipate the energy generated in saidprotective turns, said protective turns being arranged co-ncentricallyone Within another and separated by tubular insulation. and externalresistances connected parallel betvveen the protective turns, theconductors of said external resistances being concentrically related,with one conductor Within another and suitably insulated.

l2. A surge proof electro-magnetic device comprising. in combinationwith a magnetic circuit, and a Winding thereon. ofv a plurality ofprotective turns of progressively increasing capacity connectedinfseries with said Winding and wound also u'pon said circuit. andexternal resistances connected `in shuntbetu'een the protective turns,the conductors of said external resistances being concentricallvrelated. with one conductor within another and suitably insulated, andthe resistance elements comprising conducting members that are severallyattached to the tubular conductors of the resistance circuit. Withresistance elements between them.

r 13. A surge proof electrical transformer comprising. in combinationWith the magnetic circuit thereof and a high potential Winding thereon,of a plurality of protective turns wound also on said circuit and inseries with said winding, and means to dissipate the surge energygenerated in said turns.

14. A surge proof electrical transformer comprising. in combination\v-ith the magnetic circuit thereof and a high potential windingthereon. of a plurality of protective turns Wound also on said circuitand in series With saidjvinding. and external resistances connected tothe said turns to dissipate the surge energy generated in said turns.

ln testimony. that I claim the foregoing as my invention l atlix mysignature in the presence of two Witnesses. this 1st day of October. A.D. 1913. i

CHESTER H. THORDARSO. lVitnesses lV. L. HALL.

G. E. Downs.

